Allow viewer apps to run in Console sessions by lionel- · Pull Request #12545 · posit-dev/positron

lionel- · 2026-03-17T12:27:56Z

Addresses #12556

Refactored positron-run-app extension to add a new runApplicationInConsole() entry point. The internals are shared between the terminal and console paths (in particular I extracted AppUrlDetector for URL detection in app output), and now handle errors a bit more consistently.

Sessions are reused and restarted when app is started again. To make the implementation easier, positron.runtime.restartSession() now returns a boolean indicating whether the session restart was cancelled by the user. When cancelled, the app restart is cancelled too. When the session is already restarting, we wait for the restart to finish (new behaviour) and return true. These changes make the behaviour of await restartSession() clearer for callers: true result means the session is ready, false means the restart was cancelled, error means the restart couldn't be completed.
If there are breakpoints and app runner specified a debugger type, we wait for the configuration of that debugger to be done before starting the app. The configurationDone event only fires after initial setBreakpoints requests ( one per file) are successful, and this is exactly what we need to ensure that Ark's DAP has fully started up and knows about breakpoints before sourcing the Shiny app files.
The viewer's stop button gains support for console sessions. It sends console interrupts via the console service.

Once posit-dev/shiny-vscode#108 is merged and released, we can bump the bundled version and merge this PR.

Release Notes

New Features

Shiny applications are now run in console sessions instead of the terminal (Run R Shiny apps in console sessions #12556). This makes it possible to debug them with Positron's new R debugger support.

Bug Fixes

N/A

QA Notes

R Shiny apps run in console sessions, not terminals
Other apps (Streamlit etc.) still use terminals
Stop button in viewer works for console apps (interrupt) and disappears when idle (including when debugging the app, which is admitedly weird)
No breakpoints: fast startup. With breakpoints: slower but breakpoints hit
Re-running reuses the same "Shiny" console and restarts it
Re-running also reuses sessions after extension host restart or window reload
Re-running while debugging: debugger exits, session restarts
When re-running, declining the interrupt prompt cancels the restart
Closed/exited session: fresh one created on next run
Dirty document auto-saved before execution
Timeout error if URL not detected in ~25s
Rapid "Run App" clicks: "already starting" message, no duplicates

Screen.Recording.2026-03-17.at.18.38.44.mov

@:apps

github-actions · 2026-03-17T12:28:15Z

E2E Tests 🚀
This PR will run tests tagged with: @:critical @:apps

^readme ^{valid tags}

jmcphers · 2026-03-18T17:23:08Z

extensions/positron-run-app/src/api.ts

 	private readonly _runApplicationSequencerByName = new SequencerByKey<string>();
 	private readonly _runApplicationDisposableByName = new Map<string, vscode.Disposable>();
 	private readonly _appServers = new Map<string, { terminalPid: number | undefined; proxyUri: vscode.Uri }>();
+	private readonly _consoleSessionByName = new Map<string, { session: positron.LanguageRuntimeSession; listener: vscode.Disposable }>();


This needs to be stored somewhere so that we maintain the mapping between consoles and running applications when the window reloads/extension host restarts.

Done! I opted for a simple approach where we prune stale sessions from the persisting memento on each lookup. Should be fine since there should only be a handful of known sessions at any given time.

extensions/positron-run-app/src/debugAdapterTrackerFactory.ts

jmcphers · 2026-03-19T22:27:23Z

extensions/positron-run-app/src/api.ts

+			}
+		}
+		if (pruned) {
+			await this._globalState.update(PositronRunAppApiImpl.CONSOLE_SESSIONS_KEY, persisted);


Here and elsewhere: the set of console sessions should be stored in workspace state rather than global state. If they're in global state then two Positron windows opened at once will continually delete each others' entries.

https://code.visualstudio.com/api/references/vscode-api#ExtensionContext.workspaceState

Done! Thanks for walking me through all these pitfalls, first time I'm using persistent storage.

There's another failure mode though: if two different windows open the same workspace (e.g. via the duplicate command), we'd still get corruption.

It seems like the best setup for this sort of use cases would be to have storage space whose lifecycle exactly matches the console sessions (and is not persisted on disk). I've experimented with this in #12636.

Did you observe the corruption? It is not possible AFAIK to have the same workspace open in two windows. When you use the duplicate workspace command, what you get is a second (untitled) workspace with its own distinct workspace storage.

However I've been meaning to add a way for extensions to access ephemeral storage for months, and as you note it is an even better match than workspace storage since ephemeral state goes away when you close Positron. Thanks for adding that!

I didn't! Should have checked.

So that's what "duplicate" means in that command. Makes a ton of sense.

lionel- force-pushed the feature/shiny-session branch from cb587f7 to 92c5ba6 Compare March 17, 2026 16:36

lionel- mentioned this pull request Mar 17, 2026

Run Shiny app in console session in Positron posit-dev/shiny-vscode#108

Open

lionel- force-pushed the feature/shiny-session branch 3 times, most recently from e751e43 to e51c0f6 Compare March 18, 2026 10:56

lionel- marked this pull request as ready for review March 18, 2026 11:00

lionel- requested review from jmcphers and seeM March 18, 2026 11:00

jmcphers requested changes Mar 18, 2026

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lionel- force-pushed the feature/shiny-session branch from 8151db1 to 7337a79 Compare March 19, 2026 08:32

lionel- requested a review from jmcphers March 19, 2026 08:36

jmcphers requested changes Mar 19, 2026

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lionel- added 17 commits March 20, 2026 09:21

Implement Console apps

cd310d6

Handle errors at call site

60c4b74

Extract URL detection

119a093

Extract queueRunApplication()

3fa1bff

Log unhandled errors

2f59081

Throw user-visible error on timeout

615cbbc

Add stub in Python tests

e392f45

Synchronise with DAP

1aa0842

Reuse existing console sessions

77fdab5

More robust session restart

b6faa8a

Return boolean from restartSession()

dfb8296

Properly dispose of listeners

d7dc8af

Properly dispose of cancellation token

edbce69

Properly dispose of configuration listener

4017c65

Render stop button in viewer for console apps

b58883d

Only synchronize debugger when requested by app runner

4ddd485

Wait for ongoing restart in restartSession()

b28eb48

lionel- added 4 commits March 20, 2026 09:21

Synchronize d.ts files

7dc3d56

Update tests for new restartSession() resolution

b6aaaae

Persist known console sessions

8d6dbb7

Persist known consoles in workspace state

ae751a8

lionel- force-pushed the feature/shiny-session branch 2 times, most recently from 22fe806 to ae751a8 Compare March 20, 2026 09:29

lionel- mentioned this pull request Mar 20, 2026

Add ephemeral storage for extensions #12636

Open

lionel- requested a review from jmcphers March 20, 2026 15:55

jmcphers approved these changes Mar 23, 2026

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Allow viewer apps to run in Console sessions#12545

Allow viewer apps to run in Console sessions#12545
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